This invention relates in general to the field of electro-optics and, more particularly, to a method and system for testing an optical detector.
There are numerous methods and systems for detecting radiation. In one type of detector, photocathodes are used in conjunction with microchannel plates (MCPs) to detect low levels of electromagnetic radiation. Photocathodes emit electrons in response to exposure to photons. The electrons may then be accelerated by electrostatic fields toward a microchannel plate. A microchannel plate is typically manufactured from lead glass and has a multitude of channels, each one operable to produce cascades of secondary electrons in response to incident electrons. A receiving device then receives the secondary electrons and sends out a signal responsive to the electrons. Since the number of electrons emitted from the microchannel plate is much larger than the number of incident electrons, the signal produced by the device is stronger than it would have been without the microchannel plate.
One example of the use of a photocathode with a microchannel plate is an image intensifier tube. The image intensifier tube is used in night vision devices to amplify low light levels so that the user can see even in very dark conditions. In the image intensifier tube, a photocathode produces electrons in response to photons from an image. The electrons are then accelerated to the microchannel plate, which produces secondary emission electrons in response. The secondary emission electrons are received at a phosphor screen or, alternatively, a charge coupled device (CCD), thus producing a representation of the original image.
Another example of a device that uses a photocathode with a microchannel plate is a scintillation counter used to detect particles. High-energy particles pass through a scintillating material, thereby generating photons. Depending on the type of material used and the energy of the particles, these photons can be small in number. A photocathode in conjunction with a microchannel plate can be used to amplify the photon signal in similar fashion to an image intensifier tube. The detector can thus be used to detect faint particle signals and to transmit a signal to a device, e.g., a counter, that records the particle""s presence.
An optical testing system is generally used to test the detectors to ensure compliance with various operating specifications and requirements. An example optical testing system may include a cylinder coupled to a detector. One or more light bulbs may be inserted into the cylinder at various longitudinal positions along the cylinder to provide a light source for the system. For example, three light bulbs may each be inserted into the cylinder at a different longitudinal position along the cylinder. A plate configured with an aperture may also be positioned adjacent each bulb between the bulb and the detector. In operation, each of the three bulbs may be illuminated individually or in combination with other bulbs to generate up to three light intensity levels for testing the detector.
Prior systems and methods for testing a detector suffer several disadvantages. For example, testing efficiency may require the operation of several optical testing systems simultaneously, thereby allowing the testing of multiple detectors during a single test session. However, operating and/or illuminating the quantity of light bulbs required to produce various light intensity levels may be expensive and difficult to maintain. The quantity of light bulbs used to supply the various light intensity levels may also be cost prohibitive.
Additionally, simultaneously operating multiple optical test systems to test multiple detectors may require repeating various test session parameters for various detectors. For example, one or more light bulbs positioned in a cylinder of one optical test system may fail during a test session. Accordingly, the optical test system having the light bulb failure may not be capable of providing the required light intensity levels during the test session. Although the test session may continue for other optical test systems and corresponding detectors, the detector coupled to the failed optical test system may require repeating the test session to complete the required testing parameters.
Accordingly, a need has arisen for a better technique having greater flexibility and control for testing optical detectors. In accordance with the present invention, an optical testing system and method for testing optical detectors is provided that substantially eliminates or reduces disadvantages and problems associated with previously developed systems and methods.
According to one embodiment of the present invention, an optical test system for testing one or more detectors includes a signal generator operable to generate an optical signal. The system also includes an aperture system operable to regulate an intensity of the optical signal. The system further includes a signal distributor coupled to the aperture system and operable to distribute the optical signal to a plurality of optical connections. Each optical connection is coupled to a detector.
According to another embodiment of the present invention, a method for testing one or more optical detectors includes generating an optical signal using a signal generator. The method also includes regulating an intensity of the optical signal using an aperture system. The method further includes distributing the optical signal to one or more optical connections. Each optical connection is coupled to a detector.
The technical advantages of the present invention include an optical detector testing system that provides greater flexibility and reliability for testing multiple optical detectors than prior systems and methods. For example, according to one aspect of the present invention, an optical signal is generated from a signal generator and is distributed to one or more optical detectors. If the signal generator requires replacement during a testing session, the testing session may be temporarily suspended during replacement of the signal generator. Once the signal generator has been replaced, the testing session may continue. Thus, each detector that is tested using the present invention experiences a substantially complete testing session, thereby substantially eliminating a requirement of repeating the testing session for various detectors.
Additionally, the present invention provides greater flexibility than prior systems and methods by providing one or more optical signal intensity levels using a single optical signal generator. For example, according to one aspect of the present invention, an aperture system includes a plurality of shutters. Each shutter includes one or more apertures of different sizes. Various apertures of each shutter may be aligned to provide the desired optical signal intensity.
Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims.